Resistive Plate Chamber detectors are largely used in current High Energy Physics experiments, typically operated in avalanche mode with large fractions of Tetrafluoroethane (C2H2F4), a gas recently ...banned by the European Union due to its high Global Warming Potential (GWP). An intense R&D activity is ongoing to improve RPC technology in view of future HEP applications. In the last few years the RPC EcoGas@GIF++ Collaboration has been putting in place a joint effort between the ALICE, ATLAS, CMS, LHCb/SHiP and EP-DT Communities to investigate the performance of present and future RPC generations with eco-friendly gas mixtures. Detectors with different layout and electronics have been operated with ecological gas mixtures, with and without irradiation at the CERN Gamma Irradiation Facility (GIF++). Results of these performance studies together with plans for an aging test campaign are discussed in this article.
In the last few years, an intense R &D activity on particle detectors for future HEP applications has been carried on with the aim of developing new techniques as well as studying the performance of ...already existing detectors when operated in a high rate environment. As for Resistive Plate Chamber detectors, the main challenges to face are the improvement of their detection capabilities and longevity at very high-rates, and the search for new eco-friendly gasmixtures free from greenhouse components. Results obtained in the framework of the RPC ECOGas@GIF++ Collaboration on a thin-Resistive Plate Chamber exposed at the CERN Gamma Irradiation Facility and operated with eco-friendly gas mixtures based on Tetrafluoropropene and Carbon dioxide will be discussed in this paper.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Results obtained by the RPC ECOgas@GIF++ Collaboration, using Resistive Plate Chambers operated with new, eco-friendly gas mixtures, based on tetrafluoropropene and carbon dioxide, are shown and ...discussed in this paper. Tests aimed to assess the performance of this kind of detectors in high-irradiation conditions, analogous to the ones foreseen for the coming years at the Large Hadron Collider experiments, were performed, and demonstrate a performance basically similar to the one obtained with the gas mixtures currently in use, based on tetrafluoroethane, which is being progressively phased out for its possible contribution to the greenhouse effect. Long term aging tests are also being carried out, with the goal to demonstrate the possibility of using these eco-friendly gas mixtures during the whole High Luminosity phase of the Large Hadron Collider.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Resistive Plate Chambers (RPC) have shown stable operation at the Large Hadron Collider and satisfactory efficiency for the entire Run 1 (2010–2013) and Run 2 (2015–2018) with C2H2F4-based gas ...mixtures and the addition of SF6 and i-C4H10. Since its global warming potential (GWP) is high, C2H2F4 is phasing out of production due to recent European Union regulations and as a result its cost is progressively increasing. Therefore, finding a new RPC gas mixture with a low GWP has become extremely important. This contribution describes the simulation of the RPC efficiency with tetrafluoropropene C3H2F4 (HFO1234ze), a hydrofluoroolefin with very low GWP. Simulation results are systematically compared with measurements of RPC efficiency in C3H2F4-based gas mixtures with the addition of different combinations of Ar, He, CO2, O2 and i-C4H10 in various concentrations. This simulation allows the study of the interplay between C3H2F4 and the other gas components in the mixture as well as may allow the identification of the most promising environment-friendly gas mixtures with C3H2F4 for RPCs.
Gaseous detectors are widely used in high-energy physics experiments, and in particular at the CERN Large Hadron Collider (LHC), to provide tracking and triggering over large volumes. It has been ...recently estimated that Resistive Plate Chambers (RPC), used for muon detection, have the highest contribution on the overall greenhouse gas (GHG) emissions at the LHC experiments. Gas mixtures for RPCs are mainly made of C2H2F4, which is a greenhouse gas with a high environmental impact in the atmosphere. C2H2F4 is already phasing out of production, due to recent European Union (EU) regulations, and its cost is expected to increase in the near future. Therefore, finding alternative gas mixtures made of gas components with a low Global Warming Potential (GWP) has become extremely important for limiting the GHG emissions as well as for economic reasons. The novel hydrofluoroolefins are likely appropriate candidates to replace C2H2F4 due to their similar chemical structures. This study is focused on the characterization of innovative gas mixtures with tetrafluoropropene HFO1234ze(E) (C3H2F4) that is one of the most eco-friendly hydrofluoroolefins, thanks to its very low GWP. HFO1234ze(E)-based gas mixtures with the addition of Ar, N2, O2 and CO2 are extensively discussed in this paper as well as the role of i-C4H10 and SF6 in such mixtures.
The muon identification system of the ALICE experiment at the CERN LHC is based on Resistive Plate Chamber (RPC) detectors. These RPCs are operated in the so-called maxi-avalanche mode with a gas ...mixture made of tetrafluoroethane (C2H2F4), sulfur hexafluoride (SF6) and isobutane (i-C4H10). All of these components are greenhouse gases: in particular, the first gas is already phasing out of production, due to recent European Union regulations, and its cost is expected to increase in the near future. Therefore, finding a new eco-friendly gas mixture has become extremely important in order to reduce the impact of the RPC operation on the environment, and for economic reasons. Due to the similar chemical structure, hydrofluoroolefins appear appropriate candidates to replace C2H2F4 thanks to their very low GWPs, especially tetrafluoropropene (C3H2F4) with the trade name HFO1234ze(E). In order to identify an eco-friendly gas mixture fulfilling the requirements for operation in the ALICE environment in the coming years, a dedicated experimental set-up has been built to carry out R&D studies on promising gas mixtures. Measurements have been performed with a small-size RPC equipped with the front-end electronics, providing signal amplification, developed for ALICE operation at high luminosity after the LHC Long Shutdown 2. HFO1234ze(E)-based mixtures with the addition of CO2 are discussed in this paper as well as the role of i-C4H10, as quencher, and SF6, as strong electronegative gas, in such mixtures.
Due to their simplicity and comparatively low cost, Resistive Plate Chambers are gaseous detectors widely used in high-energy and cosmic rays physics when large detection areas are needed. However, ...the best gaseous mixtures are currently based on tetrafluoroethane, which has the undesirable characteristic of a large Global Warming Potential (GWP) of about 1400 and because of this, it is currently being phased out from industrial use. As a possible replacement, tetrafluoropropene (which has a GWP close to 1) has been taken into account. Since tetrafluoropropene is more electronegative than tetrafluoroethane, it has to be diluted with gases with a lower attachment coefficient in order to maintain the operating voltage close to 10 kV. One of the main candidates for this role is carbon dioxide. In order to ascertain the feasibility and the performance of tetrafluoropropene-CO2 based mixtures, an R&D program is being carried out in the ALICE collaboration, which employs an array of 72 Bakelite RPCs (Muon Identifier, MID) to identify muons. Different proportions of tetrafluoropropene and CO2, with the addition of small quantities of isobutane and sulphur hexafluoride, have been tested with 50 × 50 cm2 RPC prototypes with 2 mm wide gas gap and 2 mm thick Bakelite electrodes. In the presentation, results from tests with cosmic rays will be presented, together with data concerning the current drawn by a RPC exposed to the gamma-ray flux of the Gamma Irradiation Facility (GIF) at CERN.
The cross sections of forward emission of one, two and three neutrons by 158A GeV 115In nuclei in collisions with Al, Cu, Sn and Pb targets are reported. The measurements were performed in the ...framework of the ALICE–LUMI experiment at the SPS facility at CERN. Various corrections accounting for the absorption of beam nuclei and produced neutrons in target material and surrounding air were introduced. The corrected cross section data are compared with the predictions of the RELDIS model for electromagnetic fragmentation of 115In in ultraperipheral collisions, as well as with the results of the abrasion–ablation model for neutron emission in hadronic interactions. The measured neutron emission cross sections well agree with the RELDIS results, with the exception of In–Al collisions where the measured cross sections are larger compared to RELDIS. This is attributed to a relatively large contribution of hadronic fragmentation of In on Al target with respect to electromagnetic fragmentation, in contrast to similar measurements performed earlier with 30A GeV 208Pb colliding with Al.
Comprehensive results on the production of unidentified charged particles, π±, K±, K$_S^0$, K*(892)0, $p, \bar{p}, ϕ$(1020), Λ, Λ, Ξ-, Ξ+, Ω-, and $\bar{Ω}^+$ hadrons in proton-proton ...(pp) collisions at $ \sqrt{s}$=7 TeV at midrapidity (|y|<0.5) as a function of charged-particle multiplicity density are presented. In order to avoid autocorrelation biases, the actual transverse momentum (pT) spectra of the particles under study and the event activity are measured in different rapidity windows. In the highest multiplicity class, the charged-particle density reaches about 3.5 times the value measured in inelastic collisions. While the yield of protons normalized to pions remains approximately constant as a function of multiplicity, the corresponding ratios of strange hadrons to pions show a significant enhancement that increases with increasing strangeness content. Furthermore, all identified particle-to-pion ratios are shown to depend solely on charged-particle multiplicity density, regardless of system type and collision energy. The evolution of the spectral shapes with multiplicity and hadron mass shows patterns that are similar to those observed in p-Pb and Pb-Pb collisions at Large Hadron Collider energies. The obtained pT distributions and yields are compared to expectations from QCD-based pp event generators as well as to predictions from thermal and hydrodynamic models. These comparisons indicate that traces of a collective, equilibrated system are already present in high-multiplicity pp collisions.
The zero degree calorimeters for the ALICE experiment Puddu, G.; Arnaldi, R.; Chiavassa, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2007, Letnik:
581, Številka:
1
Journal Article
Recenzirano
The Zero Degree Calorimeters (ZDC) for the ALICE experiment will measure the energy of the spectator nucleons in heavy ion collisions at the CERN LHC, providing a direct measure of the centrality of ...the collisions. ZDC are spaghetti calorimeters, which detect the Cherenkov light produced by the shower particles in silica optical fibers embedded in a dense absorber. The main characteristics of the ZP and ZN detectors are described in this article. The calorimeters were tested at the CERN SPS using pion and electron beams with momenta ranging from 50 to
200
GeV
/
c
. Test beam results such as the calorimeter response, the energy resolution, the signal uniformity and the localizing capability are presented.
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